Synthesis of phenylacetic acids under rhodium-catalyzed carbonylation conditions

Benzyl halides are efficiently carbonylated to phenylacetic acids in the presence of a catalytic amount of the dimer of chloro(1,5-cyclooctadiene)rhodium(I) in formic acid. Under these reaction conditions, sensitive functionalities such as esters and nitriles are tolerated and the phenylacetic acids are obtained in good to high yields.